1. Field of the Invention
The present invention relates to a display, and more particularly, to device and method for compensating a picture quality of a projection type display, such as a projection TV, or a projector.
2. Background of the Related Art
A picture on the display, such as a TV receiver or a monitor, may have color, and luminance feeling of a user varied with an external illumination, that vary a user's eye tiredness. In general, the luminance of the picture has been adjusted to an optimum value according to the luminance of the external illumination for minimizing the user's eye tiredness, and a color intensity of the picture has been adjusted to an optimum value according to the color intensity of the external illumination for minimizing a variation of color feeling of the user.
The foregoing methods have been employed under the assumption that the luminance of the display, such as a TV CRT that is luminescence by itself, is basically not influenced from the external illumination at all, and what exist are only variations of luminance, and color feeling of the user caused by the external illumination. The foregoing methods have been also employed under the assumption that the TV receiver is installed close to a wall, and most of the influences from the external illumination are caused by a light incident on a front surface of the TV receiver, and a light reflected at the wall.
In the foregoing methods, the luminance and chromaticity of illumination in the vicinity of the TV receiver are calculated by an optical sensor fitted to a part of a front surface of the TV receiver, and the luminance and chromaticity of the picture are adjusted automatically according to preset luminance and chromaticity.
The foregoing methods are applicable also to a plasma display panel (PDP) or liquid crystal display (LCD) type TV receiver, because, alike the CRT type TV receiver, the plasma display panel (PDP) or liquid crystal display (LCD) type TV receiver has no variation of color reproduction characteristics of the picture itself caused by the external illumination since they reproduce a color by its own luminescence, but has variation of relative color and luminance of user caused by the external illumination only.
In the meantime, because, as typical examples of the projection type display, a projector having a projector body for providing a light inclusive of a picture and a screen for displaying the light as shown in FIG. 1, or a projection TV as shown in FIG. 2, forms the picture on the screen, not by a light emitted from the panel itself, but by a light transmitted through, or reflected at the panel, a color sense of the picture can also be varied with luminance and chromaticity of the light projected thereto, a light from an external illumination, and reflectivity and color of the screen, substantially.
However, currently, there is no technology suggested for compensating a screen luminance or a color feeling of the projection type display. The compensating methods used in the foregoing direct type display can not be applied to the projection type display because the chromaticity itself of the picture on the screen can vary with a color of the screen itself and the chromaticity of the external illumination.
Therefore, the related art projection type display has a problem in that the picture quality deterioration can not be avoided because the abnormal variation of the luminance and chromaticity of the picture caused by the external illumination and screen characteristics can not be compensated.